Purified agar silver halide photographic processing web



United States Patent 3,425,832 PURIFIED AGAR SILVER HALIDE PHOTO- GRAPHIC PROCESSING WEB Elmer S. Bornemisza, San Cabriel, Calif., assignorto Bell & Howell Company, Chicago, Ill., a corporation of Illinois No Drawing. Filed Oct. 15, 1%5, Ser. No. 496,676 US. CI. 96-61 9 Claims Int. Cl. G03c 5/30, 5/38 ABSTRACT OF THE DISCLUSURE Agar is purified by contacting a solution thereof with a cation exchange resin in sufficient quantity and for a time sufiicient to remove substantial amount of alkaline earth and heavy metal atoms. The resultant agar is used in combination with photographic processing chemicals to provide a processing Web for photographic emulsions.

This invention relatzs to the provision of material for use in photographic processes, and more particularly to the treatment of agar to make it useful as a binder for chemicals used in photographic processes.

At the present time, a two-step wet process is used to develop and stabilize an image on photographic recording media. Thus, a photosensitive silver halide emulsion, coated on paper, is exposed to a light image or signal and thereafter developed by dipping, spraying or coating with a liquid alkaline solution of developer, and stabilized by subsequent treatment with a stabilizer solution. Various one-step dry processes have been proposed which call for the application of at least one of the processing chemicals by means of a web. Thus, one or more of developer, stabilizer and alkali (which term hereinafter will be used to signify a material capable of providing alkalinity) are incorporated into a Web and are transferred by contact to the emulsion side of the photographic paper. In some methods, a developer is incorporated into the silver halide emulsion and the Web releaseably contains a stabilizer and, optionally, an alkali. In other methods the silver halide emulsion contains both developer and stabilizer, and alkali is contained in the web. Still other methods call for the incorporation of developer, stabilizer and alkali in the Web. Water-releasing agents can be incorporated in the emulsion or in the web. After imaging, the silver halide emulsion is brought into contact with the web, optionally with application of heat, and the process chemicals transfer from the Web to the emulsion, developing and/ or stabilizing the image therein.

In these methods, selection of the web binder is critical. It must be of a material that binds the process chemicals to the web support sheet and releases them when in contact with the photographic emulsion. It must not interfere with chemical reactions taking place in the emulsion and must have good coating and gelling characteristics. It must adhere to the web support sheet and hold the processing chemicals and yet be flexible enough to be bent, without cracking, and release its chemicals on pressure contact with the photographic emulsion. Various mate rials have been suggested including agar which although readily available and economical has not been used successfully as a substantial part of the gel. Agar lacks critical gelling characteristics to be an acceptable binding material. Using substantial amounts of agar, one "finds that the web does not behave predictably. When pressed in contact with a photographic gelatin emulsion, it adheres to the emulsion and does not entirely separate. Also, small amounts of impurities in the agar react with the silver halide causing erratic development and stabilization and fogging of the image.

3,425,832 Patented Feb. 4, 1969 ice It is an object of this invention to provide agar that has the required chemical and physical characteristics to be useful as a binder for photographic process chemicals. It is another object to provide a process for treating natural agar to give it such properties. It is a further object to provide a web having a binder comprising such treated agar and releasably incorporating photographic process chemicals, and which will transfer such chemicals to a photographic emulsion without inordinate adherence to the emulsion and which will not adversely react with the process chemicals or silver halide.

be above and other objects are accomplished by pro viding agar containing a reduced amount of alkaline earth and heavy metals. Such purified agar can be effectively used to bind photographic process chemicals in a web with enhanced gel properties and Without adverse interference with the development and stability of the image.

Agar (i.e., agar agar, agar kobe) is a gelatinous product extracted from algae, particularly of the Gelidium species, and from seaweeds such as Gracz'laria lichenoides, Gelidium corneum and Gigartina sp'eciosa. The agar is boiled. cooled and dried and packaged in granules, flakes, bricks or sheets. Chemically, natural agar is predominantly the calcium salt of agar acid which is polymeric with recurring 6-member ring units, each ring containing 5 carbon atoms and an oxygen atom and having hydroxy and hy droxymethyl groups attached thereto. The calcium is attached intermittently through sulfate linkages. Typically, other metals such as magnesium, potassium and sodium are, in small amounts, substituted for calcium. Heavy metal ions such as lead, copper and zinc are also present in a few hundred to a few thousand parts per million quantities.

A sample of natural agar obtained from Hathaway Allied Products, Inc., Los Angeles, California, was ana lyzed by spectrographic methods and the following metals were found in the indicated amounts:

Parts per million Calcium 84,000 Magnesium 5,300 Potassium 4,100 Sodium 2,900 Zinc 2,300 Strontium 2,300 Copper 720 Boron 500 Iron 260' Lead 230 Gold 89 Total ash 240,000

Additionally, natural agar contains a variety of low molecular weight organic impurities. I have discovered that the presence of the above alkaline earth metals, heavy metal impurities and low molecular weight organic impurities detracts significantly from the physical and chemical properties of agar and that when the amount of such impurities is substantially reduced, the resultant agar is ideally suited for use as a web binder for photographic process chemicals.

In an embodiment of this invention, the agar is purified by contacting it With a cationic exchange resin, preferably a strongly acidic type. The agar is dissolved by stirring it in an appropriate amount of boiling water. In one method, exchange resin is added and the mixture is thoroughly stirred. The resin is then removed by simple filtration. In another and preferred method, the hot agar solution is passed through a column of exchange resin. Other desired photographic process chemicals can be added to the agar solution which can then be coated on a web support sheet.

The cation exchange resin can be used in the acid form or in the salt form, e.g., the sodium, potassium or ammonium form. It is convenient to use the acid form and add a small amount of a base such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, or the like to neutralize the agar, or, if the agar is to contain alkali as a photographic process chemical, to make it somewhat basic. By using a strongly acidic cation exchange resin, calcium, magnesium and the like, as well as the heavy metals, may be replaced by sodium potassium or ammonium ions. Low molecular weight organic impurities are removed during filtration. A mixed anion and cation exchanger can also be used to remove inorganic salts and organic acid groups.

Strongly acidic cation exchange resins that can be used include the nuclear sulfonic and methylene sulfonic polystyrene and phenolic types. The most commonly available strongly acidic cation exchange resin is the nuclear sulfonic polystyrene type such as Rohm & Haas Co.s. Amberlite IR120, Diamond Alkali Co.s Duolite C-20, Dow Chemical Co.s Dowex 50-X8, Permutit Co.s Permutit Q and Nalco Chemical Co.s Nalcite HCR. Examples of methylene sulfonic phenolic type cation exchange resins are Duolite C-3 and C-10. While it is preferred to use a strongly acidic cation exchange resin, intermediate acid resins and even weakly acidic resins can be used. Examples of intermediate acid exchange resins are the phosphonic acid polystyrene types such as Duolite C62 and the phosphoric acid polystyrene types such as Duolite C-63 and Nalcite X-219. Weakly acidic exchange resins include the carboxylic acid acrylic types such as Amberlite IRC-SO and Duolite CS-lOl.

As noted, one can also use an anion exchange resin in conjunction with the cation exchange resin, particularly to aid in the removal of organic acid groups. In this respect, the weakly basic anion exchange resins are preferred including the polyamine chloromethylated polystyrene-divinylbenzene types such as Amberlite IR45, Duolite A-2, Dowex 3-X4, Permutit W, and Nalcite WBR. Intermediate base and strongly basic resins can also be used including the quaternary ammonium epoxypolyamine types such as Duolite A-3OB and Permutit A. The strongly basic anion exchange resins include the quaternary ammonium and tertiary amine chloromethylated polystyrene-divinylbenzene types such as Amberlite IRA-400, Duolite R-42, Dowex l-XS, Permutit S1 and Nalcite SBR.

The analyzed sample of natural agar described above was treated with cation exchange resin. 5 Parts of the agar were dissolved with stirring for about 15 minutes in 1,000 parts of boiling water. Parts of Amberlite IR-120 were added and stirred for about 60 minutes. The agar solution was filtered and water evaporated until the original 5 parts remained. The agar was then analyzed by spectrographic methods and the following metals were found in the indicated amounts:

Parts per million Calcium 140 Magnesium 690 Potassium 2,900 Sodium 1,300 Zinc nil Strontium 7 Copper 6 Boron 24 Iron 220 Lead nil Gold nil Total ash 17,200

Thus, the agar was substantially purified of alkaline earth and heavy metals.

In general, agar containing less than about 5,000 parts per million alkaline earth metal atoms and less than about 1,000 parts per million of heavy metal atoms are sufiiciently pure to be considered as substantially free from these atoms; however, any substantial decrease in amount of these atoms improves the properties of the agar.

To prepare webs using the purified agar of this invention, the desired photographic process chemicals can be added to the agar solution in the desired quantities and upon cooling the solution is coated upon a suitable support, e.g., paper, cloth, etc. The solution can be applied using any of the well known coating techniques. For example, a draw-down procedure with a Myer or other bar can be used; or the paper or cloth may be dipped into the agar solution and passed through rollers as a continuous strip, with subsequent cutting to the desired length.

In general, about 25 to about 75 parts, preferably about 25 to about 30 parts, by weight of agar are added per 1,000 parts of water. The amount of ion exchange resin added to the agar solution depends on the type of resin and strength. For strongly acidic resins, from about 10 to about preferably about 45 to about 55%, of the weight of the agar are added. As noted, the sodium, potassium or ammonium form of cation exchange resin can be used. If the acid form is used, an amount of base sumcient to neutralize the resin may be added. If alkali is to be incorporated into the web as a photographic process chemical then a small excess of base may be used; e.g, for sodium hydroxide about .001 to about 0.4 part per part of exchange resin may be used. For less strongly acidic resins, about 30 to about of the weight of the agar can be added. If an anion exchange resin is used, generally about 5 to about 50% of the weight of the agar can be added, depending on the basicity of the resin.

Other gelling agents may be added to the agar solution to change the properties of the web to better suit various applications. Such agents can be added in amounts up to about 20% of the weight of the agar and include polyvinyl alcohol, polyhydric alcohols (e.g., ethylene glycol, glycerol, polyethylene glycol such as Dow Polyglycol P- 400, E1450, and the like) methylcellulose, sodium alginate, dextrine, locust bean gum, dextrose, casein, and the like, or mixtures thereof. Other materials known to the art can be added to the agar solution to improve various aspects of the web and of the photographic product. Such materials include wetting agents such as Aerosol OS and OT, Nacconal NK, Nekal BA-75, Duponol ME, Spans, Tweens, and the like, and can be added in an amount up to about 0.05% of the weight of the agar. Fog reducers such as potassium bromide and Kodak Antifog #1 can be added in amounts up to about 1% of the weight of the agar.

Depending on the application, one, two or all three of alkali, developer and stabilizer are added to the web. Any conventional material may be so used. In many cases, the developer is added to the silver halide emulsion. Alkali is also added to the emulsion or may be located in the web. In some cases, the stabilizer is located in the web and released to stabilize a developed image when the web is in contact with the silver halide emulsion. In other cases, the stabilizer is located in the silver halide emulsion. The stabilizer, and optionally the developer, may be separated from the silver halide by an alkali-soluble interlayer. After imaging, by contacting the emulsion with a web of this invention containing alkali, the alkali transfers to the emulsion, dissolving the alkali-soluble interlayers, causing development and stabilization of the image. Agar contains substantial amounts of water which may be released on pressure contact and/or on application of heat.

If alkali is to be incorporated into the web, suitable materials that can be used include organic alkalies such as 1,3-propanediamine, diethanolamine, and the like; and inorganic alkalies such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphite, and the like; and mixtures thereof. In general, organic alkalies can be used in amounts up to about 800%, preferably about 150 to about 250%, of the weight of the agar. Inorganic alkalies can be added in amounts up to 50%, preferably from about 20 to about 30% of the weight of the agar.

If a fixer is to be incorporated into the web, suitable materials that can be used include thiosulfates, such as sodium thiosulfate, ammonium thiosulfate, and potassium thiosulfate; thiocyanates, such as ammonia, sodium and potassium thiocyanates; other thio derivatives, such as thiourea and thiazole; and the like, and mixtures thereof. In general, a fixer can be used in amounts up to about 500%, preferably about 150 to about 200%, of the weight of the agar.

If a developing agent is to be incorporated into the web, suitable materials that can be used include catechol, hydroquinone, toluhydroquinone, o-chlorohydroquinone, obromohydroquinone, 4-phenyl catechol, 4-t-butyl catechol, pyrogallol, 4-n-butylpyrogallol, nordihydroguiauretic acid,

4,5-dibromocatechol, 3,5,6-tribromo-4-phenylcatechol and 1 phenyl S-(N-n-hexylcarboxamine)-4-[p-(B-hydroquinoylethyl) phenylaZo]-5-pyrazolone, ascorbic acid, Phenidone B, Metol, and the like, and mixtures thereof. Developers such as Amidol (2,4diaminophenol hydrochloride) which do not require the presence of alkali to develop an image, may also be used. It may also be advantageous to add an auxiliary developing agent such as monomethyl-p-amino phenol or a 3-pyrazolidone, which appear to act synergistically in combination with a primary developer. The auxiliary agent can also be added to the silver halide emulsion with the primary developing agent being located in the web, or vice versa. In general, developing agents can be added to the web in amounts up to about 300%, preferably from about 100 to about 150%, of the weight of the agar.

The following examples, in which all parts are by weight, demonstrate and illustrate the use of agar webs of this invention.

Example 1 Gel webs were prepared as follows: 20 parts of agar kobe powder were dissolved with stirring for about 20 minutes in 750 parts of boiling water. parts of Amberlite IR-120 and 1 part of sodium hydroxide were then added and stirred for about minutes. The mixture was filtered and to the filtrate were added 40 parts of 1,3-propanediamine (alkali), 5 parts of potassium bromide and 35 parts of sodium thiosulfate (hypo). The solution was poured on a Ferro-type plate and allowed to set.

An identical agar web was prepared except that the agar-boiling water solution was not treated with ion exchange resin.

Separate sheets (A) and (B) of Plus X Reversal Film were impregnated with a solution containing 300 parts of methanol, 100 parts of water, 30 parts of ascorbic acid, 15 parts of chlorohydroquinone, 15 parts of Phenidone B, about 0.03 part of S-nitro benzoimidazole, and 4 parts of a 10% solution of polyvinyl alcohol. Several sheets of the film were exposed to a step-wedge negative using a Herrnfeld Sensitometer at 3.5 amps and developed at room temperature for 15 seconds.

One sheet of film (A) was pressed in contact with the above agar web obtained after treatment with ion exchange resin. Another sheet of film (B) was pressed in contact with the other agar web, that is the web prepared from agar not treated with ion exchange resin. Contact was made by pressing the film against the web on the Ferro-type plate for about seconds. Film A was found to be superior to film B in photographic qualities. The image was sharp and uniform. The gel uniformly adhered to the paper and was flexible and of high quality. The films were measured for fog index using a Kodak Densitometer godel RT. Film A had a 39% lower fog level than in B.

6 Example 2 To 20 parts of agar kobe powder dissolved in 750 parts of boiling water were added 10 parts of Amberlite IR-120 and 1 part of sodium hydroxide. The mixture was stirred for 30 minutes and filtered. To the filtrate were added 40 parts of 1,3-propanediamine, 5 parts of potassium bromide, 75 parts of sodium thiosulfate, 2 parts of Aerosol OS and 1 part of Kodak Antifog #1. The solution was poured on a Ferro-type plate and allowed to set.

A similar web was formulated except that treatment with ion exchange resin and sodium hydroxide was omitted.

2 sheets of Plus X Reversal Film. were developertreated and exposed as in Example 1. One sheet was pressed for about 20 seconds against the resin-treated agar web on the Ferro plate. The second sheet was similarly pressed against the agar web not treated with resin. The film stabilized with the resin-treated agar web was superior in physical properties and appearance and had a substantially lower fog index than the film stabilized by the agar web not treated with resin.

Example 3 An ion exchange column, 21 cm. long and with a 3.1 cm. inner diameter, and a glass wool bed, is prepared with Duolite C-20 cation exchange resin, in the sodium form, backwashed and compacted to 14 cm. height. A solution of 20 parts of agar kobe powder dissolved in 650 parts of hot water are passed through the column followed by parts of hot water. To the filtrate are added 30 parts of ammonium thiosulfate, 2 parts of Duponol ME and 5 parts of potassium bromide. Sheets of high wet strength polyethylene backed paper are coated with the agar solution to yield agar webs useful in stabilizing developed photographic images.

In a similar manner, agar can be treated with other cation exchange resins such as Nalcite X-219 and Duolite CS-101. With these latter resins a larger column, or a smaller quantity of agar solution, should be used.

The ion exchange resin can also be a mixture of cation and anion exchange resins such as Amberlite MB-l AR, or the filtrate may be passed through a second column containing an anion exchange resin such as Amberlite IR-45, Duolite A-30 B, or Dowex 1--X 8.

Other examples will now be apparent to those skilled in the art and changes may be made by those skilled in the art without departing from the spirit of the invention.

I claim:

1. An agar photographic silver halide processing web comprising a support and agar on said support, said agar containing less than about 5,000 parts per million of alkaline earth metal atoms and less than about 1,000 parts per million of heavy metal atoms.

2. The agar web of claim 1 additionally containing a source of alkali suflicient to activate a silver halide developer.

3. The agar web of claim 2, additionally containing a silver halide fixer in an efiective amount.

4. An agar photographic silver halide processing web comprising:

a support,

agar on said support, said agar having been purified by contact with a strongly acidic cation exchange resin, said agar containing less than about 5,000 parts per million of alkaline earth metal atoms and less than about 1,000 parts per million of heavy metal atoms, and

a water-soluble thiosulfate fixer and a source of alkali sufficient to activate a silver halide developer releaseably held in said agar.

5. The agar web of claim 4 additionally containing a small antifogging amount of potassium bromide.

6. The agar web of claim 1, additionally containing a silver halide fixer in an effective amount.

7. The agar web of claim 1, additionally containing a silver halide developer in an effective amount.

8. A process for preparing an agar photographic silver halide processing web which comprises:

dissolving agar in hot water to form a solution thereof, contacting said solution with a strongly acidic cation exchange resin, bringing said agar solution out of contact with said ion exchange resin, adding a source of alkali sufficient to activate a silver halide developer alkali to said agar solution, and coating said agar solution onto a support, said fixer and alkali being in sufficient quantity to initiate development of, and fix, an imaged developerincluded silver halide emulsion. 9. The process of claim 8 wherein said fixer is a watersoluble thiosulfate and said alkali is 1,3propanediamine.

References Cited UNITED STATES PATENTS OTHER REFERENCES Currie, T.: Ion Exchange Properties of Agar, Chem. and Ind., 1955, p. 116. CA 55:7778d.

NORMAN G. TORCHIN, Primary Examiner.

CAROLYN E. DAVIS, Assistant Examiner.

US. Cl. X.R. 96-48, 50, 63 

